The present invention is related to a vehicle designed to be employed both as a lifting machine and as an agricultural tractor.
From European Patent EP-B-375705 in the name of the same Applicant a lifting truck is known comprising a bearing structure having a central longitudinal axis, a front section and a rear section and provided with two respectively front and rear axles each having a pair of wheels; an engine unit; a control and driving cab; a telescopically extendable and retractable lifting boom arranged in proximity of the control and driving cab and having one end pivotally connected to the bearing structure around a transverse axis; and actuator means to operate swinging of the lifting boom around said transverse axis between a lowered position, in which the lifting boom is arranged substantially parallel to the longitudinal axis of the bearing structure, and a raised position.
Such vehicles equipped with a telescopic lifting boom arranged longitudinally exhibit a wide employ versatility. While its basic configuration is maintained unchanged, the vehicle can be either operated as a working machine equipped with an aerial platform adapted to be employed in the building industry and the like, or as a fork lift truck, or as a lifting machine in the most differentiated fields, etc. In the above known vehicle, whose commercial success has been and is still today remarkable, the control and driving cab is entirely located on one side of the bearing structure with respect to the longitudinal axis thereof, the engine unit is located on the opposite side of the bearing structure with respect to said longitudinal axis, and the lifting boom is arranged centrally between the control and driving cab and the engine unit, with the rear end thereof pivotally connected to the bearing structure around said transverse axis and the front end thereof designed for connection of a fork, a bucket, an aerial platform, a lifting hook, etc. thereto. The intended use of this known vehicle is thus substantially exclusively that of a lifting machine.
To the aim of further widening the fields of employ of a vehicle with a lifting boom of this type, the Applicant proposed in European Patent Application n. 98830341.8 (unpublished at the priority date of the present application) to provide the lifting vehicle with three-point hitch means and power-lift means for agricultural implements operable by means of a rear power take-off, whereby the lifting truck can thus be employed also as an agricultural tractor.
The general configuration of the vehicle remains in this case substantially unchanged with respect to the arrangement known from European Patent EP-B-375705 mentioned in the above, with its lifting boom pivotally connected at its rear end and arranged centrally between the control and driving cab and the engine unit. The three-point hitch means and the power-lift means for the agricultural implements are in fact borne by a substantially horizontal platform fixed at the rear of the vehicle bearing structure, beneath the transverse pivot axis of the lifting boom.
This so modified vehicle is thus capable of performing all functions of a conventional agricultural tractor, while affording additionally all the advantages deriving from the provision of a high-performance lifting boom. The market to which this known vehicle is mainly addressed is thus the agricultural one: however the general configuration of the vehicle, which is peculiar and relatively unique as compared with that of a conventional agricultural tractors, makes it apparently not much appreciated by the average farmer, traditionally used to operate with tractors having a familiar conventional architecture.
From this point of view a conceptually reversed approach, i.e. starting from an agricultural tractor having a substantially traditional configuration then partially transformed by the addition of a lifting boom, so as to make the agricultural tractor operable even as a lifting vehicle, would appear more efficient under the commercial standpoint. Such an arrangement is shown in European Patent Application EP-A-823367, which discloses an agricultural tractor comprising a bearing structure having a central longitudinal axis, a front section and a rear section and provided with two respectively front and rear axles each having a pair of wheels; an engine unit; a control and driving cab; a power take-off; three-point hitch means and power-lift means from agricultural implements arranged in the rear section of the bearing structure in a substantially centered position relative to said longitudinal axis; a telescopically extendable and retractable lifting boom located in proximity of the control and driving cab and having one end pivotally connected to the bearing structure around a transverse axis; and actuator means to operate swinging of the lifting boom around said transverse axis between a lowered position, in which said lifting boom is arranged substantially parallel to the longitudinal axis of the bearing structure, and a raised position, whereby said agricultural tractor is operable also as a lifting machine.
More particularly, in this known arrangement the control and driving cab is located in the rear section of the bearing structure of the tractor and is centered on the longitudinal axis thereof, immediately above the engine unit. The lifting boom is located in front of the control and driving cab, is also centered on the longitudinal axis of the bearing structure, and has its rear end pivotally connected to a transverse pin arranged in correspondence or in the area of the front wall of the structure defining the control and driving cab.
This known configuration, while been relatively more analogous to that of a conventional agricultural tractor, is affected by several drawbacks.
Firstly the arrangement of the lifting boom in front of the control and driving cab constitutes a serious obstacle to the operator""s visibility when the tractor is operated as a lifting vehicle, i.e. while the lifting boom is set in an even only partially raised position.
Secondly the location of the transverse pivot axis of the lifting boom in front of the control and driving cab involves a critical limitation to the working length of the lifting boom itself. On the other hand, in order to not excessively penalize this working length, in its lowered and retracted positions this lifting boom is necessarily protruding beyond the wheels of the tractor front axle, with evident encumbrance problems. For this reason in practice the lifting boom has to be removed when the vehicle is operated as an agricultural tractor, and is then again installed when the vehicle is instead employed as a lifting truck. Evidently installation and removal of the lifting boom require relatively long and difficult operations, also involving the provision of some auxiliary equipment.
A further inconvenience of this known vehicle resides in the uneven weight distribution on the axles thereof: the control and driving cab and the engine unit are in fact both loading the rear axle, with the further addition of the weight of the agricultural implement connected to the rear three-point hitch and related power-lift. It is believed that this load unbalance, i.e. the reduced load applied onto the front axle, may result into serious manoeuvrability difficulty of the vehicle: for this reason not only the front axle wheels but even the rear axle wheels are made steerable. The four-wheel steering system evidently involves constructive complications and consequent additional costs.
Lastly the agricultural tractor functions and the lifting machine functions, and the related devices specifically designed therefor, are completely autonomous and independent from one another. In particularly the power-lift operatively associated to the three-point hitch solely performs the task of lifting the agricultural implement when necessary, while the lifting boom carries out in turn exclusively the task of lifting the piece of equipment (fork, bucket, aerial platform, etc) applied to the front end thereof. In practice this known vehicle requires duplication of an apparatus designed for a same general function, namely that of implement lifting.
The general object of the present invention is to overcome the above drawbacks.
A particular object of the invention is to provide a vehicle operable both as a lifting machine and as an agricultural tractor whose general configuration is not much different than that a conventional agricultural tractor.
A further object of the invention is to provide vehicle operable both as a lifting machine and as an agricultural tractor which is designed to ensure, in both operating functions, the best visibility for the operator.
A further object of the invention is to provide a vehicle operable both as a lifting machine and as an agricultural tractor whose lifting boom has a greater working length and, in the lowered position thereof, does not involve any encumbrance or projection beyond the front section of the vehicle bearing structure.
A further object of the invention is to provide a vehicle operable both as a lifting machine and as an agricultural tractor having a quite balanced load distribution on both front and rear axles, so as to ensure the best manoeuvrability without any need of resorting to rear steering wheels.
Still another object of the invention is to provide a vehicle operable both as a lifting machine and as an agricultural tractor wherein the lifting function both for an agricultural implement secured to the three-point hitch and of a non-agricultural tool or device carried by the lifting boom is carried out by one single item.
According to the present invention, these objects are achieved by means of a lifting machine the main feature of which resides in that:
the lifting boom is located on one side of the control and driving cab,
the pivot transverse axis of the lifting boom is located in the front section of the bearing structure, whereby the end of said lifting boom pivotally connected to the bearing structure is the front end thereof,
the three-point hitch means are carried by the rear end of the lifting boom, and said power-lift means for agricultural implements are constituted by the lifting boom itself.
Viewed from a different standpoint, the present invention is directed to an agricultural tractor the main feature of which resides in that:
the transverse pivot axis of the lifting boom is located in the front section of the bearing structure, whereby the end of said lifting boom which is pivotally connected to the bearing structure is the front end thereof,
said three-point hitch means are carried by the rear end of the lifting boom, and said power-lift means for agricultural implements are constituted by the lifting boom itself.